This invention relates to high speed optical interconnects, particularly the class of such interconnects that include at least one optical space switch.
Satisfactory technology currently exists for impressing data on an optical carrier at bit rates of up to about 10 Gbit/s without imposing excessive current requirements upon semiconductor components used to perform the switching at these speeds. Impressing data at still higher bit rates typically involves a penalty of increased current drive requirements that, for many applications, make operation at such higher speeds unattractive with currently available technology having regard for instance to the problems of increased heat dissipation.
If it is not convenient to increase the data handling capacity of an optical link by increasing, beyond a certain upper limit, the bit rate impressed upon a single carrier on a single transmission path, then other ways must be found. One expedient that can be employed is to distribute the traffic between more than one physically discrete transmission path, such paths being operated optically in parallel. Generally however there will be a not too large number of such physically discrete optical transmission paths that can satisfactorily be accommodated, and thus another limitation is reached. It may then be possible to get round this limitation by arranging to use wavelength multiplexing to impress more than one data-bearing channel on each transmission path.
In the case of a switched optical interconnect, in which switching may for instance be effected by semiconductor optical amplifiers, the physically discrete transmission paths are optically switched by optical space switches, and it is clear that an unnecessarily large number of space switched transmission paths will contribute to unnecessary complexity and expense. On the other hand the space switching of wavelength multiplexed signals (channels) on a common transmission path imposes its own cross-talk problems associated with the non-linearities of operation of such switches. In this context it will be appreciated that when a single physically discrete transmission path is switched that contains N wavelength multiplexed signals, the power level on that switched path may lie anywhere between the level pertaining in the situation where all N channels are in their low power state, and the level pertaining when they are all in their high level state.